OBSERVATION OF THE ELASTIC FIELD RELATED TO A STRUCTURAL DOMAIN BOUNDARY ALONG A (111)NISI2 /(115)SI HETEROTWIN INTERFACE/

A (111)NiSi2//(1 (1) over bar 5)Si heterotwin interface has been obser ved by high resolution electron microscopy (HREM) along the common dir ection [(1) over bar (1) over bar 0]NiSi2//[(1) over bar (1) over bar 0]Si to identify the long period atomic structural units (ASU's). Coex istence of two different structural domains has been found with ASU's corresponding to two different cycles of five-, six-, and seven-atom r ings. A dislocation/ledge (DL) has been particularly studied because i ts separates these two unusual cycles of ASU's. The elastic displaceme nt field u of the atom columns around the DL has been calculated using both crystallographic and anisotropic elasticity properties of the cr ystals, assuming a two-dimensional u field. From a comparison between the positions of the atom columns as derived from elasticity calculati ons and as deduced from the HREM image, it is concluded that the DL is a mixed dislocation with the Burgers vector (-1/4)[111]NiSi2 +(1/2)[1 (1) over bar 0]Si = (1/12)[515]Si, a result also in agreement with th e imperceptible ledge height associated with the DL core. Such a Burge rs vector underlines the role of the Si matrix dislocations for produc ing such structural domains.